Observational Analysis and Modeling of the Land - Ocean - Atmosphere Interaction During INDOEX (1999)

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Title: Observational Analysis and Modeling of the Land - Ocean - Atmosphere Interaction During INDOEX (1999)
Author: Simpson, Matthew Drennan
Advisors: Dr. Sethu Raman, Committee Chair
Abstract: Observations from aircraft, an island station, and two research vessels are used to investigate the development of an elevated mixed layer or land plume over the Arabian sea during the Indian Ocean Experiment Intensive Field Phase 1999 (INDOEX) through air mass modification. Much of the transport of aerosols and gases occur in this plume located above a well-mixed convective marine boundary layer with a depth of 800 - 1000 m. The depth of the land plume is approximately 2000 m with the peak ozone concentrations occurring near the center of this land plume. Significant latitudinal variations in the concentration of ozone occur in the marine boundary layer and in the plume. Mean ozone concentrations in the land plume decreased with distance from the Indian coastline. The horizontal extent of the sea breeze circulation over the Arabian Sea during the Indian Ocean Experiment (1999) is investigated. Profiler data from Bombay, Goa, and Trivandrum, India show a diurnal variation in wind direction caused by land and sea breeze circulations along the west coast of India. Wind profiles taken 130 km from the west coast of India from R/V Sagar Kanya show a change in wind direction particularly at 200 to 300 m caused by the sea and land breeze circulations. Infrared satellite images show the furthest extent of the sea breeze circulation over the Arabian Sea to be around 200 km. Constant level balloons also showed the extent of the sea breeze over the ocean to be 200 km. A mesoscale numerical model was used to further investigate the horizontal extent of the sea breeze over the ocean. Simulated cross sections along the west coast of India show the horizontal extent of the afternoon sea breeze over the ocean to vary from around 130 to 200 km. Vertical velocities of around 0.20 ms-1 were produced inland as the sea breeze interacted with the mountains along India's west coast. The development and propagation of a 'pollution gradient' over the Arabian Sea during the Intensive Field Phase of the Indian Ocean Experiment (1999) is investigated. A hypothesis for the generation of the pollution gradient is presented. Infrared satellite images show the formation of the pollution gradient as the leading edge of a polluted air mass in the marine boundary layer and also its propagation over the Arabian Sea and the northern Indian Ocean. Aerosol data measured from two research vessels over the Arabian Sea show a diurnal variation in the concentrations caused by the passage of this pollution gradient. Depth of the pollution gradient was found to be about 800 m. A mesoscale numerical model was used to simulate the development of this gradient and its propagation over the ocean. Results show that its formation and structure are significantly influenced by the diurnal cycle of coastal sea-land breeze circulations along India's west coast. Transport of aerosols and gases over the Arabian Sea in the lower troposphere from land sources appears to be through this mechanism with the other being the elevated land plume.
Date: 2003-06-30
Degree: MS
Discipline: Marine, Earth and Atmospheric Sciences
URI: http://www.lib.ncsu.edu/resolver/1840.16/1721


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